The invention generally relates to lost foam patterns for two-stroke engine blocks including a cylinder having an axis. More particularly, the invention relates to arrangements for providing such a lost foam engine block pattern with a transfer passage having an arcuate outer wall which is concave in a plane parallel to a plane extending from and containing the cylinder axis, having an arcuate inner wall which is convex in cross section in a plane parallel to a plane extending radially from and containing the cylinder axis, and having two generally axially extending walls joining the inner and outer arcuate walls.
Attention is directed to the following United States Patents:
______________________________________ 4,243,093 Neiman, J. R. January 6, 1981 4,632,169 Osborn, H. L. December 30, 1986 4,640,333 Martin, et al. February 3, 1987 4,657,063 Morris, R. L. April 14, 1987 4,691,754 Trumbauer, et al. September 8, 1987 4,721,149 Hesterberg, et al. January 26, 1988 Re.31,488 Trumbauer January 10, 1984 ______________________________________
In the past, such transfer passages as described above were provided by forming the lost foam engine block pattern from three slices or pieces as shown generally in the Osborn U.S. Pat. No. 4,632,169, issued Dec. 30, 1986. In FIGS. 1 and 2 herein, the three pieces are identified by the numerals 11, 13, and 15 and the transfer passage is identified by the numeral 17. The inner and outer arcuate walls of the transfer passages are identified by the reference numerals 19 and 21. As shown, the transfer passage includes portions 31, 33, and 35, respectively located in each of the pattern portions or pieces 11, 13, and 15. The portion of the transfer passage in the piece or pattern portion 11 was provided by a die member which opened in the axial direction A. The transfer passage portion 35 provided in the pattern piece 15 was obtained by a die member which opened in the opposite axial direction B. The middle portion 33 of the transfer passage 17 was provided by a partially illustrated first die member 41 which was separated from the pattern portion 13 in the axial direction A and by a partially illustrated second die member 43 which was separated from the lost foam pattern piece or portion 13 in the axial direction B.
Thus, in the past, formation of a lost foam engine block pattern with an arcuately extending transfer passage involved formation of the pattern from three pieces and also involved formation of the transfer passage in the middle piece by two die members which cooperated with each other and which were separated in opposite directions from the lost foam middle piece 13.
The invention disclosed herein is directed to simplifying this procedure.